1. Field of the Invention
The present invention relates to an image-forming method to be used in a recording method employing an electrophotographic method, electrostatic recording method, electrostatic printing method, or toner jet system recording method.
2. Description of the Related Art
In recent years, an image-forming apparatus for an electrophotographic method, electrostatic recording method, or the like has been required to be more small-sized, light-weight, and high-speed. In order to achieve miniaturization, it is essential to reduce the diameter of a latent image bearing member, toner bearing member, or the like in an image-forming process. As the diameter of a photosensitive drum as a latent image bearing member or of a developing sleeve as a toner bearing member is reduced, the curvature of the drum or sleeve increases, so a developing zone becomes extremely narrow in a developing portion. As a result of the narrowing of the developing zone, some detrimental effects occur particularly in a jumping developing method as one dry developing method involving the use of a magnetic one-component toner (Japanese Patent Application Laid-Open No. H06-110324).
One detrimental effect due to the narrowing of the developing zone is a reduction in image density due to insufficient supply of toner. When various developing conditions such as a reduction in magnetic force of a magnet included in a developing sleeve are changed for alleviating such a reduction in density, even toner which is not sufficiently charged flies, with the result that fogging or toner scattering increases. In addition, density unevenness in association with the period of the developing sleeve (the so-called sleeve ghost) or the like is liable to occur.
In addition, some phenomena occurring in the jumping developing method owing to the narrowing of the developing zone come to be promoted. For example, an edge effect occurs in which development is carried out with magnetic toner concentrated at the edge portion of a latent image, so a transfer void occurring when a toner image formed on a photosensitive member is brought into press contact with a transfer material in the case of, for example, a contact transfer method, is liable to occur. In addition, an image is developed with magnetic toner in the form of a chain (referred to as “ear”) at the time of the development, so a phenomenon referred to as tailing is also liable to occur in which the magnetic toner protrudes from an image portion while being in an ear state.
Further, the magnetic toner is apt to receive a large stress because the number of revolutions of the developing sleeve increases in association with a reduction in diameter of the sleeve. As a result, a problem known as the so-called toner deterioration is also liable to occur: for example, a treatment agent afterward added externally to toner particles is embedded in, or eliminated from, the toner particles, or toner particle are chipped. As such deterioration proceeds, when the toner is repeatedly used, the charge quantity of the toner is lowered, or generated fine powder is stuck to the developing sleeve or a control member, with the result that an image defect in association with insufficient charging is liable to occur.
The following attempt has been made to alleviate such problems: the flowability of magnetic toner is controlled. For example, the cohesion degree of toner is adjusted (Japanese Patent Application Laid-Open No. 2003-043738), or the compressibility of toner is controlled (Japanese Patent Application Laid-Open No. 2000-181128 or Japanese Patent Application Laid-Open No. 2001-356516). However, such attempts still involve problems associated with an improvement in image quality and an improvement in durability of toner when the toner is combined with a developing sleeve with a reduced diameter.